<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .menu{
            width: 300px;
            border: 1px solid red;
           float: left;
            height: 900px;
        }
        .out{height: 1000px}
    </style>
</head>
<body>
         <div class="menu">
             <a href="p1.html" target="myframe">page1</a> <br>
             <a href="p2.html" target="myframe">page2</a> <br>
             <a href="p3.html" target="myframe">page3</a> <br>
         </div>
         <iframe  name="myframe" frameborder="1" style="width: 800px; height: 800px;"></iframe>
</body>
</html>